Calculate 9 Times the Sum of 1/3 and 1/4

Distributive Property with Mixed Numbers

Solve the following expression:

9(13+14)= 9(\frac{1}{3}+\frac{1}{4})=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Make sure to multiply the external factor by each factor in parentheses:
00:20 Let's solve each multiplication separately and then sum
00:26 Calculate 9 divided by 3
00:30 Break down 9 into 8 plus 1
00:36 Break down the fraction into whole number and remainder
00:43 Calculate 8 divided by 4
00:51 This is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following expression:

9(13+14)= 9(\frac{1}{3}+\frac{1}{4})=

2

Step-by-step solution

We'll use the distributive property and multiply 9 by each term in the parentheses:

(9×13)+(9×14)= (9\times\frac{1}{3})+(9\times\frac{1}{4})=

Let's solve the left parentheses. Remember that:

9=91 9=\frac{9}{1}

91×13=9×11×3=93 \frac{9}{1}\times\frac{1}{3}=\frac{9\times1}{1\times3}=\frac{9}{3}

Let's solve the right parentheses.

91×14=9×11×4=94 \frac{9}{1}\times\frac{1}{4}=\frac{9\times1}{1\times4}=\frac{9}{4}

Now we have the expression:

93+94= \frac{9}{3}+\frac{9}{4}=

Let's solve the left fraction:

93=3 \frac{9}{3}=3

For the right fraction, we'll separate the numerator into an addition problem:

94=8+14 \frac{9}{4}=\frac{8+1}{4}

We'll separate the fraction we got into an addition of fractions and get the expression:

3+84+14= 3+\frac{8}{4}+\frac{1}{4}=

Let's solve the fraction:

84=2 \frac{8}{4}=2

And now we obtain:

3+2+14=514 3+2+\frac{1}{4}=5\frac{1}{4}

3

Final Answer

514 5\frac{1}{4}

Key Points to Remember

Essential concepts to master this topic
  • Order: First add fractions inside parentheses, then multiply by 9
  • Technique: Use common denominators: 13+14=412+312=712 \frac{1}{3} + \frac{1}{4} = \frac{4}{12} + \frac{3}{12} = \frac{7}{12}
  • Check: Verify 9×712=6312=514 9 \times \frac{7}{12} = \frac{63}{12} = 5\frac{1}{4}

Common Mistakes

Avoid these frequent errors
  • Adding fractions without common denominators
    Don't add 13+14=27 \frac{1}{3} + \frac{1}{4} = \frac{2}{7} by adding numerators and denominators separately! This gives 9×27=247 9 \times \frac{2}{7} = 2\frac{4}{7} which is completely wrong. Always find the LCD (12) first: 412+312=712 \frac{4}{12} + \frac{3}{12} = \frac{7}{12} .

Practice Quiz

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FAQ

Everything you need to know about this question

Should I use the distributive property or add the fractions first?

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Both methods work! You can either add the fractions first then multiply by 9, or use the distributive property to multiply each fraction by 9 separately. The order of operations says parentheses first, so adding fractions first is usually easier.

How do I find the common denominator for 1/3 and 1/4?

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Find the LCD (Least Common Denominator) by listing multiples: 3: 3, 6, 9, 12... and 4: 4, 8, 12... The LCD is 12, so 13=412 \frac{1}{3} = \frac{4}{12} and 14=312 \frac{1}{4} = \frac{3}{12} .

Why is my answer a mixed number instead of an improper fraction?

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Both forms are correct! 214 \frac{21}{4} and 514 5\frac{1}{4} represent the same value. Mixed numbers are often preferred because they're easier to understand - you can see there are 5 whole parts plus 14 \frac{1}{4} more.

Can I convert everything to decimals instead?

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You could, but it's not recommended here! 13=0.333... \frac{1}{3} = 0.333... is a repeating decimal, which makes calculations messy. Working with fractions gives you the exact answer without rounding errors.

How do I check if 5¼ is really correct?

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Substitute back: 9(13+14)=9×712=6312 9(\frac{1}{3} + \frac{1}{4}) = 9 \times \frac{7}{12} = \frac{63}{12} . Convert: 6312=60+312=5312=514 \frac{63}{12} = \frac{60 + 3}{12} = 5\frac{3}{12} = 5\frac{1}{4}

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